<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta http-equiv="X-UA-Compatible" content="IE=edge" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Document</title>
    </head>
    <body>
        <script>
            //first 本身是一个函数
            const first = () => {
                return new Promise((resolve, reject) => {
                    console.log(3);
                    let p = new Promise((resolve, reject) => {
                        console.log(7);
                        setTimeout(() => {
                            console.log(5);
                            resolve(6);
                        }, 0);
                        resolve(1);
                    });
                    resolve(2);
                    p.then((arg) => {
                        console.log(arg);// 1
                    });
                });
            }

            first().then((arg) => {
                console.log(arg); // 2
            });
            console.log(4);
        </script>
    </body>
</html>
